Apparatus for multiplexing between on-board units in a vehicle

ABSTRACT

A multiplexing apparatus multiplexes between processing units and a battery unit of a vehicle which are connected to one another by wire harnesses, by grouping a variety of on-board controlled objects into a plurality of neighboring controlled objects and controlling each of respective processing units. The wire harness has electric conductors of which the outer peripheral portion are covered with a first insulating layer, electric conductivity layer which covers the electric conductors, a second insulating the peripheral portion of the electric layer which covers conductivity layer, means for applying an electric potential to said electric conductivity layer, and means for monitoring the electric potential of said electric conductivity layer.

This application is a continuation of application Ser. No. 08/604,613,filed Jan. 23, 1998, which is a continuation of Ser. No. 08/604,613,filed Feb. 21, 1996.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for multiplexing betweenon-board units of a vehicle by using wire harnesses.

Recently, various controls in a vehicle are performed by an on-boardcomputer and the associated electrically controlled equipments. Thus,large amounts of electric wiring are used in the vehicle. The electricwiring, such as the wire harnesses, have the potential for causing ashort-circuit. Therefor, various apparatus for detecting theshort-circuit of wire harnesses for power supply have been proposed inthe past.

One of them is disclosed in Japanese Patent publication No. 4-17809(1992), in which the rated consumption currents for respective loads arecalculated in advance, the occurrence of an abnormality due to theshort-circuit is detected by comparing the sum of the rated consumptioncurrents with the sum of the current one in the vehicle.

However, when a wire harness is installed into a vehicle body, theharness may be jammed into the vehicle body and/or the coating of theharness may be broken due to the rubbing of the harness on metalportions of the vehicle body. Therefore, a core wire of an electricpower source may short to a ground portion of the vehicle body, and thusserious accidents such as a fire in the vehicle may break out in theworst case.

In the above prior art, the apparatus is constructed such that theserious accidents can be prevented immediately by cutting off the wholecurrent. Therefore, when such accidents occur during driving, a powersource is cut off. As a result, the vehicle stops suddenly. Further,when the driver changes the load of an electric system, it is requiredto change the predetermined rated value. Therefore, there was apossibility that a malfunction would occur. In addition, while theshort-circuit of the wire harness can be detected, the processing afterthe detection of the short-circuit can not be performed.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an apparatus formultiplexing between on-board units of a vehicle, which apparatus candetect at an early stage the short-circuit of the wire harness.

Another object of the present invention is to provide an apparatus formultiplexing between on-board units of a vehicle, which apparatus canperform a suitable processing when the short-circuit of the wire harnessis detected, thereby the serious accident can be prevented in advance.

In order to achieve the above objects, an electric conductivity layer isprovided outside the electric wires, and the predetermined electricpotential is provided to the electric conductivity layer. Further, theoutside of the electric conductivity layer is covered with an insulatorlayer. As a result, a sub-wire harness is formed as a whole. The wireharness in the whole vehicle is constructed by connecting the sub-wireharnesses to each other by a connector. The multiplexing apparatusincludes, besides a monitor for monitoring an electric potential of thewire harness and detecting a short-circuit to the ground, a controlsystem for determining the short-circuit on the basis of the result ofthe detection by the monitor, and an alarm raising system for raising analarm according to a command from the control system, and a circuitbreaker to break the current from a power source.

According to one aspect of the present invention, the multiplexingapparatus multiplexes between processing units and a battery unit of avehicle which are connected to one another by wire harnesses, bygrouping a variety of on-board controlled objects into a plurality ofneighboring controlled objects and controlling each of the groups byrespective processing units. The wire harness has electric conductors ofwhich the outer peripheral portion are covered with a first insulatinglayer, electric conductivity layer which covers the electric conductors,a second insulating layer which covers the peripheral portion of theelectric conductivity layer, device for applying an electric potentialto said electric conductivity layer, and a monitor the electricpotential of said electric conductivity layer.

Preferably, the electric conductivity layer is formed by a thin meshwire.

The multiplexing apparatus according to the present invention furthermay include an alarm for raising an alarm to a driver, and a controlsystem for starting up the alarm to raise the alarm.

In addition to the alarm and the control system, the multiplexingapparatus further may include a power source circuit breaker for cuttingoff a current supplied from the battery unit, wherein said controlsystem start up said power source circuit breaker to cut off the currentfrom the battery, when said electric conductivity layer isshort-circuited to the ground.

In the multiplexing apparatus according to the present invention, theremay be provided a plurality of electric conductivity layers betweenwhich insulating layers are sandwiched alternately.

Preferably, the multiplexing apparatus further may include an alarm forraising an alarm to a driver, a power source circuit breaker for cuttingoff a current supplied from the battery unit, and a control system forstarting up said alarm to raise the alarm and starting up said powersource circuit breaker to cut off the current from the battery unit,when at least one of said electric conductivity layers isshort-circuited to the ground.

Preferably, the multiplexing apparatus further include a device forapplying an electric potential to said electric conductivity layer, amonitor the electric potential of said electric conductivity layerbetween respective groups, a detector for detecting the short-circuit ofthe wire harness to the ground on the basis of the output of saidmonitor, and a circuit breaker for cutting off a current passing throughsaid electric conductor from the power source when the short-circuit ofthe wire harness to the ground is detected by said detector.

The above multiplexing apparatus further may include a data storage forstoring the data used to estimate the damage by using at least one ofthe frequency of the short-circuit of the wire harness to the ground,the term of time of the short-circuit, the position of the short-circuitand the importance as parameters, and a control system for setting thecondition of cut-off of the circuit breaker on the basis of the datastored in the data storage.

Preferably, the multiplexing apparatus according to the presentinvention further includes a device for applying an electric potentialto said electric conductivity layer, a monitor for the electricpotential of said electric conductivity layer between respectiveprocessing units, a detector for the short-circuit of the wire harnessto the ground on the basis of the output of said monitor, and an alarmfor raising the alarm to a driver when the short-circuit of the wireharness to the ground is detected by said detector.

In the multiplexing apparatus described above, the electric potentialapplying device preferably include a C-shaped electric conductivity bodya portion of which is notched, an electric conductor connected to theelectric conductivity body, for detecting an electric potential, and apull-up resistor, and wherein said electric conductivity body ispress-bonded to the electric conductor from the outside of the electricconductivity layer of the thin mesh wire.

It is desirable to provide data storage for storing the data used toestimate the damage by using at least one of the frequency of theshort-circuit of the wire harness to the ground, the term of time of theshort-circuit, the position of the short-circuit and the importance asparameters, and a control system for changing a alarm level of the alarmon the basis of the data stored in the data storage.

Further, the power source cut-off preferably includes a switchingelement.

The multiplexing apparatus according to the present invention furthermay include a fail-safe device which allows the processing unit incharge of the group of the area where the abnormality occurred to notifythe occurrence of the abnormality to a processing unit of another groupwhen said wire harness becomes abnormal, cut away the abnormal area andleave the control to the processing unit of another group.

Preferably, in the multiplexing apparatus according to the presentinvention, the processing units include a terminal processing unit whichperforms only the processing at the associated group, and a control unitwhich performs all the processing including the processing of theterminal processing unit.

In operation, the outermost insulating layer of the wire harnessfunctions as a protecting layer, and it prevents the power source linefrom the ground-short. When the insulating layer is broken and itreaches the electric conductivity layer, the electric potential of theelectric conductivity layer changes. Therefore, it is possible todetermine the presence or absence of the short-circuit by detecting thechange. When the short-circuit is detected, it becomes possible toperform the predetermined processing by the processing unit in charge ofthe group to which the short-circuited wire harness belongs. Because theelectric conductivity layer is formed by a thin wire mesh, there is notalmost the fear of disconnection due to external force. It is,therefore, possible to maintain stable performance.

More practically, the control system starts up the alarm when theelectric conductivity layer is short-circuited to the ground, and thusthe alarm is raised. As a result, it is possible to alert the driver.

Further, the control system starts up the power source circuit breakerwhen the electric conductivity layer is short-circuited to the ground,and thus a current from the power source is cut off. As a result, it ispossible to prevent a vehicle fire due to the short-circuit.

Furthermore, because a plurality of electric conductivity layers areprovided for the detection of a short-circuit, the control systemdetermines whether only an alarm is raised or the power source is alsocut off in addition to the alarm. Therefore, it is possible to take asuitable counter-measure according to the position where theshort-circuit occurs.

Further, the monitor monitors the electric potential applied to theconductivity layer, and the detector detects the short-circuit of thewire harness to the ground on the basis of an output of the monitor.When the detector detects the ground-short, the circuit breaker cuts offthe power source. At that time, the control system grasps the state ofthe ground-short from data to estimate damage by using the parameters ofthe frequency of the short-circuit of the wire harness to the ground,the time period of the short-circuit, the position of the short-circuitand its importance, and sets the condition for the cut-off of the powersource. Therefore, it is possible to take the most suitablecounter-measure in accordance with the state of the ground-short.

Further, the monitor monitors the electric potential applied to theconductivity layer, and the detector detects the short-circuit of thewire harness to the ground on the basis of an output of the monitor.When the detector detects the ground-short, the alarm raises an alarm.At that time, the control system grasps the state of the ground-shortfrom data to estimate damage by using the parameters of the frequency ofthe short-circuit of the wire harness to the ground, the time period ofthe short-circuit, the position of the short-circuit and its importance,and changes the level to raise the alarm so as to raise the mostsuitable alarm in accordance with the state of the ground-short.

When the abnormality conditions such as the ground-short occurs, theprocessing unit in charge of the group in the area where the abnormalityoccurred notifies the occurrence of the abnormality to a processing unitof another group, and cuts away the abnormal area to maintain safety. Atthat time, because the control which has been performed by theprocessing unit in charge is left to the processing unit of anothergroup, the effect due to the cut-away of the abnormal area iseffectively suppressed.

The multiplexing apparatus includes a terminal processing unit whichperforms only the processing at the associated group, and a controlprocessing unit which performs all the processing including theprocessing of the terminal processing unit.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference numerals denote like parts in thevarious views.

FIG. 1 is a perspective view showing the configuration of a wire harnessused in an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a short-circuit detecting circuitusing the wire harness shown in FIG. 1.

FIG. 3 is a perspective view showing a tape formed by a conductor memberfor detecting the short-circuit and an insulator member used in anotherembodiment of the present invention.

FIG. 4 is a perspective view showing the structure of the wire harnessin which the tape shown in FIG. 3 is wound around electric conductorwires.

FIG. 5 is a view showing the structure of the conductor member fordetecting the short-circuit and an insulator member used in a furtherembodiment of the present invention.

FIG. 6 is a view showing the structure of the conductor member fordetecting the short-circuit and an insulator member used in a furtherembodiment of the present invention.

FIG. 7 is a schematic view of a connector for fixing the conductormember and connecting it the conductor wire.

FIG. 8 is a schematic view showing the structure of the wire harness towhich the structure shown in FIG. 7 is applied.

FIG. 9 is a perspective view showing the structure of the wire harnesswhich has a double structure made of the conductor member and theinsulator member.

FIG. 10 is a circuit diagram showing the short-circuit detecting circuitusing the wire harness with the structure shown in FIG. 9.

FIG. 11 is a circuit diagram showing an example of an alarm system forground-short using the wire harness with the structure shown in FIG. 9.

FIG. 12 is a flow chart showing the procedure of processing in the alarmsystem for a ground-short using the wire harness with the structureshown in FIG. 9.

FIG. 13 is a circuit diagram showing a lighting circuit for an on-boardlamp using the wire harness with the function of detection of theshort-circuit used in the present invention.

FIG. 14 is a circuit diagram showing the internal construction of acontroller shown in FIG. 13.

FIG. 15 is a block diagram showing an example in which the wire harnesswith the function of detection of the short-circuit is applied to amultiplex communication system used in a vehicle (In-vehicle LAN).

FIG. 16 is a flow chart showing the procedure of communicationprocessing in an In-vehicle LAN shown in FIG. 15.

FIG. 17 is a flow chart showing the procedure of processing in asub-routine of the processing shown in FIG. 16 carried out at the timeof the cable short-circuit.

FIG. 18 is a view showing the relationship between points, and place,frequency and importance in the subroutine of step S41 of FIG. 17.

FIGS. 19a and 19 b are illustrations showing an example in which theconductor member for detection of the short-circuit having a resistancevalue is wound on a cylindrical form.

PREFERRED EMBODIMENTS OF THE INVENTION

Embodiments of the present invention will be explained hereinafter withreference to the drawings.

FIG. 1 shows the structure of a wire harness according to the presentinvention. Electric wires 3, 4 and 5 are covered with an insulatinglayer, and further covered with an electric conductor member 2 for thedetection of a short circuit. The wire harness 1 is formed by coveringthe outside of the conductor member 2 with an insulating member 6. Theinsulating member 6 protects the conductor member 2 for the detection ofshort-circuits and the electric wires 3, 4, 5, and ties them together ina bundle. In addition, the insulating member 6 protects the conductormember 2 from short-circuiting to the ground of a vehicle. An electricconductor wire 7 is provided for the connection to external equipment.The wire harness according to this embodiment has the structuresubstantially identical to a three-core shield wire. Therefore, in thisembodiment, the electric wires 3, 4, 5 function as electric conductivitymeans, and one of three electric wires acts as an electricalcommunication wire. Further, the conductor member 2 for the detection ofshort-circuit functions as an electric conductivity layer and theinsulating member 6 functions as an electrically insulating layer.

FIG. 2 shows an example of a short-circuit detecting circuit. In FIG. 2,an electric potential is applied through a pull-up resistor R1 to theconductor member 2 for the detection of a short-circuit connected to a +(plus or positive) terminal of a comparator 8. The voltage divided byresistors R and r is applied to a − (minus or negative) terminal of thecomparator 8.

v=V*r/(R+r)  (1)

An output S1 of the comparator 8 indicates a high level when theshort-circuit detecting conductor member 2 is at a normal state, or whenit is not short-circuited to the ground. While, the output S1 indicatesa low level when the conductor member 2 is short-circuited to theground, for example, due to the damage of the insulating member 6. Itis, therefore, possible to detect the short-circuit of the wire harnessto the ground by monitoring the output of the comparator 8. In thisembodiment, the pull-up resistor R1 acts as a device for applying anelectric potential to the electric conductivity layer, and thecomparator acts as a monitor for the electric potential.

FIG. 3 shows another embodiment of the wire harness according to thepresent invention, which shows in detail a portion of the short-circuitdetecting conductor member and the insulating member. The insulatingmember 9 is made of a flexible member such as a vinyl tape, inside ofwhich a conductor member 10 is embedded. An adhesive agent 11, inaddition to the insulating member 9 and the conductor member 10, forms atape 12 wound around the wire harness. By forming the wire harness insuch a way, it becomes easy to detect the short-circuit, because theelectric potential of the conductor member 10 drops to the groundpotential when the ground-short occurs by the breakage due to therubbing of the insulating member 9.

FIG. 4 shows the structure of the wire harness in which the tape 12shown in FIG. 3 is wound around the conductor wires 3, 4 and 5. Theshort-circuit detecting circuit has the same construction as that shownin FIG. 2. The winding of the tape 12 may be overlapped, or may not beoverlapped.

FIG. 5 shows a further embodiment of the present invention, which showsthe structure of the conductor member for detecting the short-circuitand the insulator member. In FIG. 5, the insulator member 13 is made ofa flexible insulating member such as a vinyl tape. A conductor member 14inside of the insulator member 13 is made of a flexible conductivitymember such as an aluminum tape. The electric wires 3, 4, 5 are coveredin order by the conductor member 14 and the insulating member 13thereon. Further, there is no problem even if a different conductor orinsulating member is provided between the electric wires 3, 4, 5 and theconductor member 14. The short-circuit detecting circuit has the sameconstruction as that shown in FIG. 2.

FIG. 6 shows the structure of the conductor member for detecting theshort-circuit and insulator member used in a further embodiment of thepresent invention. In FIG. 6, the insulator member 13 is made of aflexible insulating member such as a vinyl tape. The conductor member 14inside of the insulator member 13 is made of a flexible conductivitymember such as an aluminum tape. The electric wires 16, 17, 18 arecovered in order by the conductor member 14 and the insulating member 13thereon. In this embodiment, the electric wires 16, 17, 18 are printedon a flexible substrate 19. The short-circuit detecting circuit has thesame construction as that shown in FIG. 2.

FIG. 7 shows a connector for fixing the conductor member 14 andconnecting it to the conductor wire 7. As shown in FIG. 7, the connector15 has a structure such that the conductor wire 7 is connected to aring-shaped conductor member 20 with a partially cut-away portion 20 a.

FIG. 8 shows the construction of the wire harness to which the connector15 shown in FIG. 7 is applied. In FIG. 8, the connector 15 is made byattaching and swaging the ring-shaped conductor member 20 around theconductor member 14 of the wire harness 1, thereby holding a sufficientconnection between the wire harness and the conductor member 20. Thepartially cut-away portion 20 a is provided to ensure the margin forswaging. The connection provides the conductivity between the conductormember inside the insulating member 13 and the conductor member 20 ofthe connector 15. Thereby, the electric potential is applied to theconductor member 14 through the conductor wire 7 connected to theconductor member 20. Further, the connector 15 also acts to bind theelectric wires 3, 4, 5 and the conductor member 14.

FIG. 9 shows the structure of the wire harness which has a doublestructure made of the conductor member and the insulator member. A firstinsulating member 21 at the outermost periphery of the wire harness isused for protecting the whole wire harness. While a first conductormember 22 in the outer periphery is used as a detector for theground-short of the wire harness, only alarm is raised even if theconductor member 22 short-circuits, because a second conductor member 14and a second insulating member inside the first conductor member areprovided. A conductor wire 23 is used for applying an electric potentialto the first conductor member 22. If the second insulating member 13suffers damage after the damage of the first conductor member 22, andthe second conductor member 14 short-circuits to the ground, the insidewires 3, 4, 5 may suffer damage in a short time. Therefore, the driveris alerted to the abnormality in another way apart from the alarm. Theconductor wire 7 is used for applying an electric potential to thesecond conductor member 14. While in this example the conductor membersand the insulating members are combined in double, it is possible tocombine them more than double layers.

FIG. 10 shows the short-circuit detecting circuit using the wire harnesswith the structure shown in FIG. 9. In FIG. 10, an electric potential V1is applied through a pull-up resistor R1 to the first conductor member22 connected to a + (plus) terminal of a comparator 24. As describedwith respect to the equation (1), the voltage divided by resistors R andr is applied to a − (minus) terminal of the comparator 24. An output S1of the comparator 24 indicates a high level when the first conductormember 22 is at a normal state, or when it is not short-circuited to theground. While, the output S1 indicates a low level when the firstconductor member 22 is short-circuited to the ground, for example, dueto damage of the insulating member of the first conductor member 22.

Further, an electric potential V2 is applied through a pull-up resistorR2 to the second conductor member 14 connected to a + (plus) terminal ofa comparator 25. As described with respect to equation (1), the voltageobtained by dividing the voltage V by resistors R and r is applied to a− (minus) terminal of the comparator 25. An output S2 of the comparator24 indicates the high level when the second conductor member 14 is at anormal state, or when it is not short-circuited to the ground. While,the output S1 indicates the low level when the second conductor member14 is short-circuited to the ground, for example, due to the damage ofthe insulating member of the second conductor member 14.

It is, therefore, possible to detect the ground-short of the wireharness including its risk by monitoring the outputs of the comparators24 and 25.

FIG. 11 is a circuit diagram showing an example of an alarm system for aground-short using the double-layer type wire harness with the structureshown in FIG. 9. In FIG. 11, a current from the power source is suppliedfrom a − (minus) terminal of the battery through link 31 and emergencycutoff relay 32 to other loads. The current from the power source isalso supplied through a fuse 34 and a regulator 35 to the control systemor a processor 33. The short-circuit of the first conductor member 22 isdetected by the first comparator 24, and the short-circuit of the secondmember 14 is detected by the second comparator 25. Outputs of thosecomparators are input to the processor 33. The processor 33 processesthe outputs according to the procedure shown in FIG. 12, and determinesthe risk of short-circuit. Namely, when the first conductor member 22 isshort-circuited, an alarm lamp is lighted and caution is given to adriver. When the second conductor member 14 is short-circuited, it isdetermined that the wire harness will become dangerous, and a driver 37is cut off and thus the relay 32 is cut off. As a result, the wholepower for the vehicle is cut off.

Referring now to FIG. 12, FIG. 12 is a flow chart showing the procedureof processing in the alarm system for ground-short using the wireharness with the double-layer structure shown in FIG. 9. In step S1, anoutput of the first comparator (A) 24 is checked, which detects theshort-circuit of the first conductor member 22. If the output is at thelow level, then the processing advances to step S7. In step S3, anoutput of the second comparator (B) 25 is checked, which detects theshort-circuit of the second conductor member 14. If the output is at thehigh level, then it is determined that the wire harness isshort-circuited, and a counter B for the detection of the short-circuitof the first conductor member 14 is incremented in step S4. If theoutput is at the low level, then the process advances to step S5. Instep S5, the value of the counter B is compared with the predeterminedthreshold value N2. If the value of the counter B is equal to or largerthan the predetermined threshold value N2, then it is determined thatthe short-circuit of the second conductor is deteriorated. In step S6, amain relay 32 for the power source is cut off and the system is shutdown. While, if the value of the counter B is smaller than thepredetermined threshold value N2, then the process returns to START.

Further, if the output of the second comparator (B) is at the low levelin step S3, then the value of the counter (A) is compared with thepredetermined threshold value N1 in step S8. In this case, if the valueof the counter (A) is equal to or larger than the value N1, then it isdetermined that the short-circuit of the first conductor 22 isdeteriorated. In step S9, a warning flag is indicated and the alarm lampis lighted. If the value of the counter (A) is smaller than the valueN1, then the process is returned to START. In step S7, it is checkedwhether or not the first conductor member 22 is short-circuited. If thefirst conductor member 22 has already been short-circuited, then theprocess advances to step S3, and if it has not been short-circuited,then the process returns to START.

FIG. 13 shows a lighting circuit for an on-board lamp using the wireharness with the function of detection of the short-circuit used in thepresent invention. A current from the battery 30 is controlled by aswitch 40 and a lamp load 41 is turned on or off. Wires are connectedthrough connectors 42 and 43. Short-circuit detecting conductor members44, 45, 46, 47 are connected between the battery 30 and the connector42, between the connector 42 and the controller 48, between thecontroller 48 and the connector 43, and between the connector 43 and thelamp 41, respectively. Namely, the conductor members 44 to 47 areelectrically connected to a single controller (control system) 48. Wheneach of the short-circuit detecting conductor members is short-circuitedover the predetermined times, the alarm is raised by an alarm lamp 49connected to the controller 48.

FIG. 14 shows the internal construction of the controller shown in FIG.13. In the controller 48, there are provided comparators 51 to 54 in thecontroller 48, which check output voltages of the short-circuitdetecting conductor members 44 to 47. When the wire harnesses are notshort-circuited, voltages V1 to V4 are applied through pull-up resistorsR1 to R4 to + (plus) input terminals of the comparators 51 to 54,respectively. An electric potential of the plus input terminal is atground when the wire harnesses are short-circuited. The voltage obtainedby dividing a voltage V by using resistors R and r as shown in theequation (1) is applied to − (minus) input terminal. An output of eachof the comparators is input to a CPU 55. When the output at the highlevel occurs over the predetermined times, it is assumed that theconductor member is short-circuited to the ground. As a result, thealarm lamp is lighted.

FIG. 15 is a block diagram showing an example in which the wire harnesswith the function of detection of the short-circuit is applied to amultiplex communication system used in a vehicle (hereinafter, referredto as an In-vehicle LAN). The In-vehicle LAN comprises one BCM (BodyControl Module—control processing unit) 102, a first, a second and athird LCU (Local Control Unit —terminal processing unit) 103, 104, 105,a first, a second and a third combination cable (wire harness) 107, 108,109, each of which is connected between the processing units, a fourthcombination cable 106, and a battery 101 connected through the fourthcombination cable 106 to the BCM 102. This In-Vehicle LAN system is aso-called “central control” type of In-Vehicle LAN.

A buzzer 110 and a first and a second lamp 111, 112 are connected to aBCM 102. A power cable (the fourth combination cable) connected betweenthe battery 101 and the control processing unit BCM 102 is constructedas a combination cable of a communication wire and a short-circuitdetecting wire harness.

The first LCU 103 is connected through the first combination cable 107to the BCM 102. The first LCU 103 is also connected to a first and asecond motor 113, 114, and a first and a second operating switch 119,120 each for operating these motors 113, 114. The second LCU 104 isconnected through the second combination cable 108 to the first LCU 103.The second LCU 104 is also connected to a third and a fourth motor 115,116, and a third and a fourth operating switch 121, 122. The third LCU105 is connected through the first combination cable 109 to the secondLCU 104. The third LCU 105 is also connected to a third and a fourthlamp 117, 118.

The BCM 102 transmits and receives data through combination cables toand from the first LCU 103 and the third LCU 105, and outputs a commandsignal to control an actuator connected to each of LCUs 103 to 105 onthe basis of information obtained from the first, the second, and thethird LCUs 103, 104, 105 through electrical communication.

There are provided the first to the fourth operation ˜wit˜h˜s 119 to 122the buzzer 110, the first to the fourth lamps 111, 112, 117, 118, thefirst to the fourth motors 113 to 116 in the neighborhood of a pluralityof electric equipments in the system. They are connected to any one ofthe first to the third LCUs 103 to 105 and the BCU 102. Further, theshort-circuit detecting circuits or the combination cables 106 to 109are incorporated in the BCU and the LCUs 103 to 105. The BCM 102 detectsthe short-circuit of the fourth combination cable, the first LCU 103 thefirst combination cable, the second LCU 104 the second combinationcable, and the third LCU 105 the third combination cable.

A brief explanation of a series of data transmissions will be givennext. When the BCM 102 transmits a certain data to an LCU, the LCU whichreceived the data answers the input data itself back to the BCU.Therefore, first, a data transmission signal directed from the BCU 102to any one of the LCUs 103 to 105 appears in a communication wire of thecombination cable, and then a data reception signal directed from anyone of the LCUs 103 to 105 to the BCM 102 appears in the samecommunication wire. A set of transmission and reception signals asdescribed above are supplied to other LCUs in the same way. The dataanswered to the LCU 103 to 105 is input to a self-contained load controlunit, and operates actuators such as the motors 113 to 116. Further,signals indicative of the state of various operating switches 119 to 122are answered to the BCM 102, which the LCUs 103 to 105 input. Thesesignals indicate the required operation.

FIG. 16 is a flow chart showing the procedure of the whole communicationprocessing. The communication processing shown in FIG. 16(a) expressesthe processing steps in which the BCM 102 communicates with the LCUs103, 104 and 105, and BGJ (Back Ground Job) shown in FIG. 16(b) is theassembly of processing 1 (step S31) to processing n (step S3n) todetermine how to control on the basis of the reception data. The BGJprocessing is endless processing performed when other processing is notperformed. For example, if it is required to perform the communicationprocessing when the processing 1 (step S31) is now performing, thecommunication processing is performed after the communication processing1 (step S31) is temporarily interrupted, and the processing 1 isperformed from the point where the processing 1 is interrupted before.

The communication processing is reception interruption processingperformed when the reception data from the LCUs 103 to 105 reaches theBCM 102. In this processing, the data from LCUs 103, 104, 105 is firstreceived in step S21. After that, it is checked whether or not thecombination cables 106 to 109 are short-circuited in step S22. If it isdetermined that a short-circuit occurred in the combination cables, thenthe processing after the short-circuit of the cable is performed in stepS23. The next LCU to be accessed is selected in step S24 and the data istransmitted to the selected LCU in step S25. While, if in step S22, itis determined that no short-circuit occurred, then the next LCU to beaccessed is selected in step S24 without performing the processing afterthe cable short-circuit, and the processing for the data transmission isperformed in step S25.

FIG. 17 is a flow chart showing the procedure of processing carried outat the time of the cable short-circuit. In step S41, the position ofoccurrence of the short-circuit in the combination cables 106 to 109 isidentified. As described above, because the BGM 102 and each of the LCUs103 to 105 detect the short-circuit of the combination cables 106 to109, it is possible to easily detect which combination cable isshort-circuited. After the short-circuit of the combination cables isdetected, the number of occurrences of the short-circuit is detected.Where, the number of occurrences per unit time is expressed asfrequency. Next, the importance, that is, the extent of whether or notthe failure caused by the short-circuit extends to safety componentssuch as a head-light, is detected. These detected data are used asparameters in the calculation of points. The points are calculated byusing a map as shown in FIG. 18, and the total points indicate the levelof emergency. In other words, the processing in step S41 indicates theextent of the state of the currently occurring short-circuit.

When the emergency level is calculated as described above, levels 1 to 4are selected according to the calculated level in step S42. Thisprocessing is temporary alarm processing. If the conditions with respectto the points are satisfied, or the ignition key is turned on, then thealarm indicative of these conditions is raised just once. When the totalpoints are equal to or more than 15 and less than 20, the processingcorresponding to the emergency of level 2 is performed in step S44. Thisprocessing is continuous alarm processing. In this case, the alarm israised continuously or interruptly. Therefore, the alarm is givenearlier to a driver. When the total points are equal to or more than 20and less than 40, the processing corresponding to the emergency of level3 is performed in step S45. In this processing, a downstream currentfrom the power source to the LCUs 103 to 105 is cut-off upstream of theposition where the short-circuit of the combination cable is occurred,and the continuous alarm is raised in step 46 in a manner similar tothat of Step 44. Because the current from the power source is cut off atthe position of the occurrence of the short-circuit, it becomes possibleto prevent the worst condition which causes vehicle fire even if theshort-circuit is deteriorated, and confirmly raise an alarm to a driver.Next, when the total points are equal to or more than 40, the processingcorresponding to the emergency of level 4 is performed in step S47. Thisprocessing is performed in such a case that the short-circuit of thecombination cable may occur at the position nearer the battery 101. Inthe level 4, the entire power source in the LAN system is cut off,thereby preventing the occurrence of fire from the short-circuit. Whenthe total points are less than 5, no processing is performed.

By performing the processing described above, it is possible to alert adriver to the occurrence of a short circuit and further repair, andprevent the occurrence of a vehicle fire in advance, because the powersource is cut off in the case where the short-circuit occurs frequently.It should be appreciated that it is possible to cut away only the cableat the position where the short-circuit occurs such that the electricpower can be supplied from another circuit by using a looped combinationcable. Further, the position where the short-circuit occurs can beeasily known through the LAN communication. Furthermore, because theoccurrence of the short-circuit is transmitted to each of the LCUs 103to 105, at the occurrence of the short-circuit, it is possible to carryout special control processing, for example, to neglect data obtainedfrom the position where the cable is cut away and the estimation of suchdata. Further, Because the LAN system grasps the conditions ofoperation, it is possible to detect the short-circuit of a wire harnessalso during driving or parking. Therefore, in case the wire harness isshort-circuited due to external vibration, it is possible to instantlycut off the power source.

FIG. 19 is an illustration showing an example in which the conductormember 60 for detection of the short-circuit having a resistance value A(Ω/m) is wound on a cylindrical body with radius R. FIG. 19(a) shows theform of the wounded conductor member, and FIG. 19(b) shows therelationship between the angle to be wound and the width of theconductor member. Assuming that the width of the conductor member is dand the conductor member is wound around without a gap, then:

cos φ=d/4R

Therefore, the value of the resistor R0 per one round is

π/2

R0=4R∫∫{square root over ( )}(1+(cot φ)² (sin θ)²)dθ*A

0

When the voltage V is applied to the conductor member by using thepull-up resistor R2, the electric potential Vx is:

Vx=V*R0*N/(R0*N+R2)

where, N is a turn number.

The determination of the position where the ground-short is occurred iscalculated by measuring the Vx and obtaining the N.

Namely,

N=R2/R0*Vx/(V−Vx)

Accordingly, it is possible to determined the position where theground-short is occurred.

What is claimed is:
 1. An apparatus for multiplexing between processingunits and a battery unit of a vehicle which are connected to one anotherby a wire harness, by grouping a variety of controlled on-board objectsinto a plurality of neighboring controlled objects and controlling eachof the groups by respective processing units, in which said wire harnesscomprises: electric conductors, each having an outer peripheral portioncovered with a first insulating layer, electric conductivity layer whichcovers said electric conductors, a second insulating layer which coversthe outer peripheral portion of said electric conductivity layer, meansfor applying an electric potential for monitoring shorting to saidelectric conductivity layer, and means for monitoring the electricpotential of said electric conductivity layer with respect to groundvariations of said electric potential indicating shorting between saidelectric conductivity layer and ground, whereby potential failure insaid electric conductors is anticipated.
 2. A multiplexing apparatusaccording to claim 1, wherein said electric conductivity layer is formedby a thin mesh wire.
 3. A multiplexing apparatus according to claim 1,further comprising alarm means for raising an alarm to a driver, andcontrol means for starting up said alarm means to raise the alarm.
 4. Amultiplexing apparatus according to claim 3, further comprising a powersource circuit breaker for cutting off a current supplied from thebattery unit, wherein said control means start up said power sourcecircuit breaker to cut off the current from the battery, when saidelectric conductivity layer is short-circuited to the ground.
 5. Amultiplexing apparatus according to claim 1, wherein there are provideda plurality of electric conductivity layers between which insulatinglayers are alternately sandwiched.
 6. A multiplexing apparatus accordingto claim 5, further comprising: alarm means for raising an alarm to adriver, a power source circuit breaker for cutting off a currentsupplied from the battery unit, and control means for starting up saidalarm means to raise the alarm and starting up the power source circuitbreaker to cut off the current from the battery unit, when at least oneof said electric conductivity layers is short-circuited to ground.
 7. Amultiplexing apparatus according to claim 1, further comprising: meansfor monitoring the electric potential of said electric conductivitylayer between respective groups, means for detecting the short-circuitof the electric conductivity layer to the ground on the basis of theoutput of said monitoring means, and circuit breaker for cutting off acurrent passing through said electric conductor from the power sourcewhen the short-circuit of the electric conductivity layer to the groundis detected by said detecting means, whereby potential failure of saidelectric conductor is anticipated.
 8. A multiplexing apparatus accordingto claim 1, further comprising: means for monitoring the electricpotential of said electric conductivity layer between respectiveprocessing units, means for detecting the short-circuit of the electricconductivity layer to the ground on the basis of the output of saidmonitoring means, and alarm means for raising an alarm to a driver whenthe short-circuit of the electric conductivity layer to the ground isdetected by said detecting means, whereby potential failure of saidelectric conductor is anticipated.
 9. A multiplexing apparatus accordingto claim 4, wherein said power source cutting-off means include aswitching element.
 10. An apparatus for multiplexing between processingunits and a battery unit of a vehicle which are connected to one anotherby a wire harness, by grouping a variety of controlled on-board objectsinto a plurality of neighboring controlled objects and controlling eachof the groups by respective processing units, in which said wire harnesscomprises: electric conductors, each having an outer peripheral portioncovered with a first insulating layer, electric conductivity layer whichcovers said electric conductors, a second insulating layer which coversthe outer peripheral portion of said electric conductivity layer, meansfor applying an electric potential for monitoring shorting to saidelectric conductivity layer, means for monitoring the electric potentialof said electric conductivity layer with respect to ground variations ofsaid electric potential indicating shorting between said electricconductivity layer and ground, whereby potential failure in saidelectric conductors is anticipated, means for monitoring the electricpotential of said electric conductivity layer between respectiveprocessing units, means for detecting the short-circuit of the electricconductivity layer to the ground on the basis of the output of saidmonitoring means, and alarm means for raising an alarm to a driver whenthe short-circuit of the electric conductivity layer to the ground isdetected by said detecting means, whereby potential failure of saidelectric conductor is anticipated; wherein said electrical potentialapplying means comprise a C-shaped electric conductivity body having aportion which is notched, an electric conductor connected to theelectric conductivity body for detecting an electric potential, and apull-up resistor, and wherein said electric conductivity body ispress-bonded to the electric conductor from the outside of the electricconductivity layer which is a thin mesh wire.
 11. An apparatus formultiplexing between processing units and a battery unit of a vehiclecoupled to one another via wire harnesses, by grouping a variety ofcontrolled on-board objects into a plurality of neighboring controlledobjects and controlling each of said groups by respective ones of saidprocessing units, in which at least one of said wire harnessescomprises: electrical conductors having an outer peripheral portioncovered with a first insulating layer; an electric conductivity layercovering said electrical conductors, wherein an electrical potential formonitoring shorting is applied to said electric conductivity layer; asecond insulating layer covering an outer peripheral portion of saidelectric conductivity layer; and an electric potential monitoroperatively connected to said electric conductivity layer for detectingshort circuits of said electric conductivity layer to ground, whereby apossible occurrence of a short circuit of said electric conductors isanticipated.
 12. A multiplexing apparatus according to claim 11, furthercomprising: an alarm circuit coupled to an alarm indicator for a vehicledriver; and a processor for activating the alarm circuit to raise thealarm indicator for the driver.
 13. A multiplexing apparatus to claim12, further comprising: a power source circuit breaker operativelyarranged so as to cut-off a current supplied from the battery unit;wherein said processor starts up the power source circuit breaker tocut-off the current from the battery when the electric conductivitylayer is short-circuited to ground.
 14. A multiplexing apparatus toclaim 11, wherein said electric potential monitor monitors the electricpotential of the electric conductivity layer between respective groups;a short-circuit detector coupled to the wire harness for detecting ashort circuit of the electric conductivity layer to ground on a basis ofan output from the monitor; and a circuit breaker for cutting-off acurrent passing through said electric conductor from the battery unitwhen the short-circuit of the electric conductivity layer is detected.15. An apparatus for detecting a short circuit of a wire harness for apower supply used in a motor vehicle, the wire harness comprising:electrical conductors having an outer peripheral portion covered with afirst insulating layer; an electric conductivity layer covering saidelectrical conductors, wherein an electrical potential for monitoringshorting is applied to said electric conductivity layer; a secondinsulating layer covering an outer peripheral portion of said electricconductivity layer; and an electric potential monitor operativelyconnected to said electric conductivity layer for detecting shorting ofsaid electric conductivity layer to ground, whereby a potentialoccurrence of a short in said electric conductor is anticipated.